The Associated Press is standing by its reporting that Sen. Richard Burr (R-NC) recently told supporters privately that he would support self-described Democratic socialist Bernie Sanders over GOP contender Sen. Ted Cruz.

Cruz has become such a pariah that one of his colleagues, Sen. Richard Burr of North Carolina, told supporters at a campaign fundraiser for his own re-election that he would vote for liberal Sen. Bernie Sanders for president before Cruz, according to one person who attended the event.

Burr did not appear to be joking, said the person, who demanded anonymity to discuss the private gathering.

The North Carolina lawmaker is vociferously refuting the report. On Twitter he voiced his objections and, according to the Charlotte Observer, officially requested the AP retract the story.

Burr is facing reelection this year. One of his primary opponents, Greg Brannon, slammed Burr in a press release saying the incumbent went “full socialist.”

“Richard Burr has long been one of the House of Cards Republicans in Washington, going along with the liberal and socialist programs and policies put forth by Democrats,” Brannon said in a statement. “Of course he would prefer an avowed Socialist to a man like Ted Cruz who has stood up to the Washington Establishment.”